1. Field of the Invention
The present invention relates to the transfer of liquid into or out of a closed container and particularly to facilitating the withdrawal of potable liquid from a canteen by an individual wearing a protective mask which isolates the individual's breathing passages from the ambient atmosphere. More specifically, this invention is directed to a tube arrangement defining a pair of parallel flow paths which respectively include oppositely directed check valves and especially to a drinking tube assembly which facilitates the employment of a closed canteen by an individual wearing a protective face mask. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in establishing liquid flow communication between a protective respiratory mask and a canteen.
There may, of course, be occasions where it is necessary to allow an individual wearing a protective mask to drink from a canteen or other closed liquid storage container. In the past, communication between the interior of the mask and canteen has been established by means of a single tube. The single tube drinking system has a number of inherent disadvantages. Firstly, the canteen must be raised at least to the level of the mask in order to obtain liquid flow. Also, with the single tube system, as liquid is withdrawn from the canteen a vacuum is created therein. The vacuum, in turn, limits the amount of liquid which can be withdrawn. Thus, for each swallow, the user must expend the effort of sucking liquid through the tube and, subsequent to drinking, must blow back into the canteen to pressurize the canteen, thus allowing more fluid to exit.
A further disadvantage of the prior single tube system is that the canteen cannot be completely filled with the cap on, as may be necessary to prevent contamination, because a positive pressure will build up inside the canteen thus limiting the amount of liquid which can be delivered thereto.